<!DOCTYPE html>
<html>
<head>
  <style>
  body { font-size: 10px; font-family: Arial; }
  h1, h2 { margin: 3px 0; }
  </style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
  <h1 style="background:#ccc;color:blue;">Header 1</h1>

  <p>Contents 1</p>
  <h2 style="background:#ccc;color:blue;">Header 2</h2>
  <p>Contents 2</p>
<script>$(":header").css({ background:'#CCC', color:'blue' });</script>

</body>
</html>